Hello Fbsd, thanks for contacting us through the Intel Communities.
First of all I suggest you backing up all the data before performing any change on your array. Since you had a RAID 1, but you reinstalled the OS on one of the hard drives, please save the information from the other hard drive.
In order to rebuild your RAID, you need to boot to Windows or to the Operating system you are using. Then, install the Intel® Rapid Storage Technology, version 11.7 https://downloadcenter.intel.com/Detail_Desc.aspx?DwnldID=22194
The following URL will guide you into the process of rebuilding your RAID1.
Fbsd, I would recommend you using the Intel® Rapid Storage Technology since this is the new version of Intel Matrix storage manager.
I want to be sure on something, do you or you don’t want to save the information from the hard drive #2?
If you do please follow these steps:
1. It will be necessary to save the data locate on HDD#2 into another disk.
2. Connect HDD#1, select that disk in order to boot to windows.
3. Rebuild the RAID using the Intel® Rapid Storage Technology. This procedure will erase all the information from disk #2 and copy the data that is on disk #1.
4. Then, you would have to copy de information from the extra hard drive into the RAID.
If you don’t want to save the data, you just need to follow steps #2 and 3.
In order to select the correct hard drive to boot to Windows, in our motherboard we use the F10 key. Please check with Gigabyte which “F” key do they use for this action.